1. Field of the Invention
This invention relates to the splicing of thermoplastic yarns, and in a further aspect relates to an apparatus for heat-splicing thermoplastic yarns and tapes.
2. The Prior Art
Thermoplastic yarn can be made by a number of methods including, for example, extrusion of relatively large diameter monofilaments or the extrusion of very small diameter filaments which are then entangled and/or twisted together to form larger diameter yarns. Thermoplastic yarns can also be made by extruding narrow films (or tapes) or extruding films and cutting the films into tapes. The tapes are then twisted into yarns. Such yarns are frequently used in the manufacture of carpets. The manufacture of fibrillated tapes which can be twisted into such yarns is, for example, described in my U.S. Pat. No. 3,496,259. Splicing can be used to repair yarns as a result of inadvertent breaks as when too much tension is applied at the ends, or as a purposeful occurrence to form longer yarn lengths. Also in many instances, such as for example in carpet tufting it is desirable to tuft continuously in order to maximize production. Thus, it is desirable to splice roll ends together to avoid having to shut down the tufting operation to rethread new rolls when the existing rolls are used up.
Numerous methods have been used by the art to splice yarns. For example, published German Patent application DT No. 2,450,018, discloses a trigger actuated splicer utilizing a hot wire to cut yarn ends and to provide heat for fusing the yarns together. U.S. Pat. No. 3,492,181 discloses a gun-shaped splicing device utilizing V-shaped holder jaws and a hot-wire cutting-fusing operation. U.S. Pat. No. 3,294,614 discloses a splicer using a rotary action to bring the yarns in contact with a heating coil to fuse the yarns together and U.S. Pat. No. 2,863,492 discloses a splicing device using a heat bonded adhesive to splice the yarns. As pointed out in my prior U.S. Pat. No. 4,138,308, yarn splicing is not a simple matter because the splice must meet both strength and bulk limitations. More specifically the shear strength of the spliced tapes must not fall below a set value, for example, generally about 3 lb. tensile pull for a 1700-denier yarn; and the all-over diameter or maximum transverse width must not adversely effect the utilization of the yarn, for example, where the yarn is used for carpet tufting, the splice must be below the minimum eyelet size of the tufting needles later used in tufting carpet to prevent the yarn splice from binding in the needle. Also, the splicer should be easily handleable and effect the splicing operation as a simple continuous mechanical operation with minimum operator involvement so as to reduce human error to a minimum. Thus, even though numerous prior art methods are disclosed, there is substantial room for improvement in one or more of these areas depending upon the particular prior art splicing method or device used.